@AndyZ19 wrote: I’m having this same problem. It’s horroble. New tv, got the newest box. Built in apps are perfect but trying to watch on xfinity it looks like SD almost.
the 4k TV has 4 times as many pixels to fill as a 1k 1080p screen. The set top box or the TV or a combination of both are enlarging the picture to fit the screen. When you change/add an HDMI device it will be necessary to set up the HDMI connected device. One way is to use the Netflix app within the X1 with 4K service and search for 'test patterns'. find one that is for 4k and let it run (audio off) for a minute or so to get up to full resolution connection. then set up the sharpness/contrast/brighttness/gamma.
The cable channels from networks is in 720p60 as are many local channels. the other channels are in lower resolution 1080i (interlaced) format. you might want to try putting the cable box into 720p and let the TV handle the upscaling (to 1080p for example). you can put in 4k mode when watching netflix 4k titles.
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